Justin -
"This review is from: Nintendo 3DS, N3DS - Li-ion Ultimate Long Life Extended Battery with cover - 5000mAh
One of the few flaws with the 3DS is its Battery Life, but this Battery fixes that problem wonderfully. Admittedly it makes the 3DS thicker & heavier, but that is a small price to pay to enable it to function for extended periods away from a power source, which then enables full use of its features.

Got mine from the £10.99 Amazon seller, took a lot longer to charge (as expected) but the battery is lasting ages, normally have to charge it every other day, but has lasted much, much longer. It is heavier, but doesn't look too bad. Does mean I can keep the streetpass/wifi on all the time so more likely to pick up more hits for the quest for hats :)